Passive Routing for Reporting and Other Read-Only Workloads | Teradata Unity - 17.00 - Passive Routing for Reporting and Other Read-Only Workloads - Continuous Availability - Teradata Unity

Teradata® Unity™ User Guide

Product
Continuous Availability
Teradata Unity
Release Number
17.00
Published
September 2020
Language
English (United States)
Last Update
2020-09-15
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Passive routing is the most basic form of connectivity provided with Unity. It allows a client session to connect to a single specified Teradata system. Requests are then sent to that system. Optionally, the routing rule can also define a set of failover servers, so that if the first system is not available, the session reconnects to the next available system in the set.

Reporting applications and other workloads often use volatile tables for temporary storage of selected data. This data is used only for the lifetime of the workload and is discarded when the workload completes. These types of workloads generally use a passive routing rule. The passive routing option provides the following benefits.
  • Volatile tables are only created on one system.
  • Queries that access the tables are sent only to the system.
  • With only one set of data generated (on a single system), it does not matter if the data generated is deterministic across multiple systems.
  • Requests from passive routing rules are never recorded in the recovery log, never affect the Unity data dictionary, or update the unitymgmt transaction table, processing time.

There are five types of passive routing rules.

Routing Rule Description
Single-System Specifies only a single system

If that system is not available, the clients using this routing rule cannot connect. Use this option for business users that do not require any failover capability or for Database Administrators that need to connect to a specific system to perform maintenance.

Preferred Specifies that the first system in the routing list is the preferred system

It is used if available. If it is not available, the session connects to the next available system in the routing rule system list.

Least-Used Allows the client to connect to a set of two or more Teradata systems

When the client connects, it is sent to the system that currently has the least number of passive connections. Use this option to makes sure the systems are evenly balanced when the sessions are running different loads.

Round Robin Allows the client to connect to a set of two or more Teradata systems

When the client connects, it is sent to the first system. The next session is sent to the second system, and so on. Use this option when each session is expected to execute the same amount of work.

Weighted Round Robin Allows the client to connect to a set of two or more Teradata systems, but in a weighted ratio specified by the routing rule

Use this option when working with systems that are sized differently and can support a different number of connected sessions.